后台 performFetchWithCompletionHandler 使用 Blocks 导致崩溃

Question

我有一个应用程序可以成功获取并显示我想要添加后台获取的 RSS 源。我收到：线程 1 EXC_BAD_ACCESS（代码=1，地址=0x10），如下所示。

在应用委托中：

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    //setup background fetch
[application setMinimumBackgroundFetchInterval: UIApplicationBackgroundFetchIntervalMinimum];

return YES;

}

        //background fetch new RSS Feeds
-(void)application:(UIApplication *)application performFetchWithCompletionHandler:(void (^)(UIBackgroundFetchResult))completionHandler
{
    NSLog(@"performFetchWithCompletionHandler");
    UIStoryboard *mainStoryboard = [UIStoryboard storyboardWithName:@"Main" bundle:nil];
    MasterViewController *navigationController = [mainStoryboard instantiateViewControllerWithIdentifier:@"MasterView"];
    MasterViewController *viewController = navigationController;

    [viewController fetchNewDataWithCompletionHandler:^(UIBackgroundFetchResult result) {
        completionHandler(result);
    }];
}

在我的主要ViewController:

@property (nonatomic, copy) void (^completionHandler)(BOOL);
- (void) fetchNewDataWithCompletionHandler: (void (^)(UIBackgroundFetchResult))completionHandler;
- (void) startParsingWithCompletionHandler:(void (^)(BOOL))completionHandler;

-(void)fetchNewDataWithCompletionHandler:(void (^)(UIBackgroundFetchResult))completionHandler{

self.completionHandler = UIBackgroundFetchResultNewData; //completionHandler;
[self startParsingWithCompletionHandler:^(BOOL success){

    if (success) {
        completionHandler(UIBackgroundFetchResultNewData);
        NSLog(@"completionHandler");
    }
    else{
        NSLog(@"error");
    }
}];

}

    - (void) storyIsDone//called when parser completed one rss feed
{
    numberOfCompletedStories ++;
    if (numberOfCompletedStories == self.rssFeedAddresses.count)
    {
            //if all the feeds are done cancel time-out timer
        [NSObject cancelPreviousPerformRequestsWithTarget: self selector: @selector(stopParsing) object: nil];
        [self.activityIndicator stopAnimating];
        storysAreLoading = NO;
        [self.refreshControl endRefreshing];
        [[NSNotificationCenter defaultCenter] addObserver: self selector: @selector(reloadRSSfeeds) name: @"ReloadFeeds" object: nil];
        canRefresh = YES;
        NSLog(@"call back");
        self.completionHandler (YES);//crash here:  Thread 1 EXC_BAD_ACCESS (code=1, Address=0x10)
    }//else not yet complete
}

我收到的输出是：

performFetchWithCompletionHandler

回调

Answer 1

self.completionHandler = UIBackgroundFetchResultNewData;

不匹配类型。 completionHandler 是 (void (^)(UIBackgroundFetchResult)) 类型，而 UIBackgroundFetchResultNewData 是 NSUInteger.

类型

typedef enum : NSUInteger {
   UIBackgroundFetchResultNewData,
   UIBackgroundFetchResultNoData,
   UIBackgroundFetchResultFailed 
} UIBackgroundFetchResult;

所以当你调用 self.completionHandler (YES) 时，self.completionHandler 是一个 NSUInteger，所以 NSUInteger(YES) 没有多大意义。

Answer 2

试试这个：创建一个变量 var completionHandler:((UIBackgroundFetchResult)->Void)! 当您收到推送通知集时

self.completionHandler = completionHandler.

然后执行后台操作，通常是从服务器下载新数据。完成后，像这样调用 completionHandler：

if let handler = self.completionHandler{
    UIBackgroundFetchResult.NewData
}
self.completionHandler = nil

那么你应该去掉那个警告。

后台 performFetchWithCompletionHandler 使用 Blocks 导致崩溃

Background performFetchWithCompletionHandler using Blocks causes crash

ios

objective-c

objective-c-blocks

background-process